“I decided to make my own version of an arduino person counter after viewing Login258 tripwire and electro18 IR person counter. This is a great device that can be used to count the number of people who visit a store, detect if a soccer ball complete passed over a goal line, or even security. Additionally, two such setups could be used to construct a speedometer to measure the speed of cars down a one lane road. There are a number of devices that you could make with this or by making minor adjustments to the setup.”